Abstract
Knowledge of the interactions between nanomaterials and large-size mammalian cells, including cellular uptake, intracellular localization and translocation, has greatly advanced nanomedicine and nanotoxicology. Imaging techniques that can locate nanomaterials within the structures of intact large-size cells at nanoscale resolution play crucial roles in acquiring this knowledge. Here, the quantitative imaging of intracellular nanomaterials in three dimensions was performed by combining dual-energy contrast X-ray microscopy and an iterative tomographic algorithm termed equally sloped tomography (EST). Macrophages with a size of ∼20 µm that had been exposed to the potential antitumour agent [Gd@C82(OH)22] n were investigated. Large numbers of nanoparticles (NPs) aggregated within the cell and were mainly located in phagosomes. No NPs were observed in the nucleus. Imaging of the nanomedicine within whole cells advanced the understanding of the high-efficiency antitumour activity and the low toxicity of this agent. This imaging technique can be used to probe nanomaterials within intact large-size cells at nanometre resolution uniformly in three dimensions and may greatly benefit the fields of nanomedicine and nanotoxicology.
Highlights
Nanotechnology has dramatically increased the intentional and unintentional exposure of humans to nanomaterials, which generate various biological effects
By combining scanning transmission X-ray microscopy (STXM) and a Fourier-based iterative tomographic algorithm termed sloped tomography (EST), we investigated the quantitative threedimensional subcellular distribution of Gd@C82(OH)22 within a macrophage
Schematic layout of the dual-energy imaging technique. (a) Two sets of projections were acquired by STXM at energies below and above the absorption edge of a specific element, (b) the projections were reconstructed by the equally sloped tomography (EST) algorithm separately and (c) the quantitative threedimensional distribution of the specific element was calculated based on the abrupt change in the absorption
Summary
Nanotechnology has dramatically increased the intentional and unintentional exposure of humans to nanomaterials, which generate various biological effects. The observed differences between images collected at the two energies reflect the locations of element-specific nanomaterials (Zhang et al, 2010; Rarback et al, 1987) This method has been widely applied to many fields to investigate biological materials (Wang et al, 2015; Conesa et al, 2016; Chen et al, 2014), organic materials (Johansson et al, 2007; Hitchcock et al, 2008), energy materials (Nelson et al, 2011; Liu et al, 2014; Kao et al, 2013; Andrews & Weckhuysen, 2013) and clinical medical applications (Houk et al, 1979; Lewis, 1997). By investigating the subcellular distribution of this nanomedicine, we hope to improve our understanding of the antitumour activities of this agent
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